In modern internal combustion engines, devices for the variable adjustment of the control times of gas exchange valves are used to be able to vary the phase relation between the crankshaft and camshaft in a defined angle range between a maximum advanced position and a maximum retarded position. The device is integrated in a drive train by means of which torque is transmitted from the crankshaft to the camshaft. This drive train can be realized, for example, as a belt, chain, or gearwheel drive. In addition to the camshaft, the device has a phase adjustment device and a central screw by means of which the phase adjustment device is locked in rotation with the camshaft. The phase adjustment device can be constructed, for example, as an oscillating drive in a vane cell construction with several pressure chambers acting against each other. By adding pressurized medium to a group of pressure chambers while simultaneously discharging pressurized medium from the other group of pressure chambers, the phase relation of the impeller relative to the cell wheel and thus the camshaft relative to the crankshaft can be varied. The pressurized medium flow to and from the pressure chambers is typically regulated by means of a hydraulic proportional directional control valve that can be mounted, for example, within the central screw.
Such a device is known, for example, from DE 10 2005 060 111 A1. In this embodiment, the central screw is screwed with a solid camshaft, in order to realize the rotationally locked connection between the phase adjustment device and the camshaft.
From DE 10 2004 026 863 A1, another device is known. In this embodiment, the phase adjustment device is mounted on an installed camshaft that consists of a tube and cams attached to this tube. In this embodiment, the attachment of the phase adjustment device to the camshaft can be realized only with difficulty due to the camshaft constructed as a hollow tube. For this reason, the phase adjustment device is locked in rotation on the camshaft by means of a weld connection.
Another device is known from DE 102 28 354 A1. In this embodiment, a hollow space that is used as a volume accumulator is provided within the solid camshaft. In operating phases of the internal combustion engine in which sufficient pressurized medium is made available from a pressurized medium pump of the internal combustion engine for operating the phase adjustment device, the volume accumulator fills with pressurized medium. If the demand for pressurized medium of the phase adjustment device increases past the volume flow provided by the pressurized medium pump, the volume accumulator supports the phase adjustment device.